Stacking device

ABSTRACT

A device for stacking bags at the outlet of a bag-forming machine, comprising a conveying belt, control means imparting an intermittent movement thereto, a stop extending cross-wise to the belt movement direction and control means for imparting an alternating motion thereto to release a bag stack for conveying by said belt, and means bearing on said bag stack during forming thereof with a contacting part moving together with said bag stack.

United States Patent [191 Van de Gent [451 Feb. 25, 1975 STACKING DEVICE[75] Inventor: Edouard Louis Van de Gent, Meise,

Belgium [73] Assignee: Printex,Neder-Over-Heem, e um.

[22] Filed: Sept. 15, 1972 [21] Appl. No.: 289,620

[30] Foreign Application Priority Data Sept. 15, 1971 Belgium .,....772622 [52] U.S. Cl. 93/93 DP, 93/93 C, 271/46 [51] Int. Cl. B3lb l/98[58] Field of Search... 93/93 R, 93 C, 93 M, 93 DP;

[56] References Cited UNITED STATES PATENTS 1,655,804 l/l928 Zuckerman93/93 DP Harnberger et al. 93/93 DP 2,761,361 9/1956 3,585,709 6/1971Carrel 93/93 DP X 3,587,410 6/1971 Dechanciaux 93/93 DP UX 3,596,5758/1971 Brockmuller 93/93 DP Primary Examiner-Andrew R. Juhasz AssistantExaminer-Leon Gilden Attorney, Agent, or F irm-Cushman, Darby & Cushman[57] ABSTRACT A device for stacking bags at the outlet of a bagformingmachine, comprising a conveying belt, control means imparting anintermittent movement thereto, a stop extending cross-wise to the beltmovement direction and control means for imparting an alternating motionthereto to release a bag stack for conveying by said belt, and meansbearing on said bag stack during forming thereof with a contacting partmoving to- I gether with said bag stack.

14 Claims, 3 Drawing Figures PATENIED FEB2 51975 sum 2 or '3 PATENIEBFEB 2 5 I975 SHEET 3 0F 3 STACKING DEVICE This invention has for objecta device to be arranged at the outlet of a machine, particularly amachine for shaping plastic bags, said device being so designed as toallow on the one hand the formation of a bag stack and on the other handthe removal of the formed bag stack, said device comprising an endlessconveying belt on which the bags are stacked, control means to impart tosaid belt an intermittent movement through either a bag-countingapparatus or an apparatus measuring the bag stack height, a stopextending cross-wise to the belt movement direction and against whichthe bag stack is formed, and control means synchronized with the beltcontrol means for imparting to the stop an alternating motion so as torelease the formed bag stack and allow the removal thereof by said belt.

Devices of this kind presently known have the drawback that when the bagstacks are released by the movable stop and taken along by the endlessbelt, said bag stacks spread on said belt under the combined action ofinertia and of the lack of adhesion of the material used. It is thusnecessary for the person who checks the bag stacks at the outlet fromthe device, to reform said stacks before packaging same. If such astackreforming job may be considered as possible at the outlet fromlow-output bag-forming machines, it is not the case with high-outputmachines where it is necessary to have two operators to release in duetime the bags from the device and to reform the bag stacks.

The invention has for object to obviate said drawback and to provide astacking device which allows whatever be the production rate of thebag-forming machine, to retain the bags perfectly arrayed in stacks downto the outlet of said device where said stacks may be released manuallyby a single operator or taken over mechanically to be conveyed to someother place.

For this purpose according to the invention, said device comprises meansso arranged as to bear on the upper side of the bag stack by the momentwhere said stack is formed, control means being provided to impart tosaid means an alternating motion to move same towards and away from saidupper side, said bearing means being so arranged that the part thereofengaging the bag stack upper side moves with the same linear speed asthe endless belt and along the same direction as said belt.

In a further embodiment of the invention, second control means areprovided to positively drive the bearing means with the same linearspeed as the endless belt and along the same direction as said belt.

In an advantageous embodiment, the control means for the stop and thecontrol means for moving said bearing means towards or away from the bagupper side are synchronized and comprise a single driving member, saidcontrol rneans being so arranged that the bearing means bear on the bagstack upper side by the moment where the stop retaining said stack hasbeen completely separated from the endless belt and has released the bagstack.

In a particularly advantageous embodiment of the invention, the endlessbelt control means and the bearing means second control means comprise asingle driving member for driving the belt and said means along the samedirection and with the same linear speed.

Other details and features of the invention will stand out from thedescription given below by way of non limitative example and withreference to the accompanying drawings, in which:

FIG. 1 is an elevation view with parts broken away of the deviceaccording to the invention.

FIG. 2 is a diagrammatic plain view of the device shown in FIG. 1.

FIG. 3 is an elevation view with parts broken away of another embodimentofthe device shown in FIG. 1.

In the various figures, the same reference numerals pertain to similarelements.

The device according to the invention and shown in FIGS. I and 2 is tobe arranged at the outlet of a machine for forming plastic bags (notshown) so as to allow the formation of a bag stack and the removal ofthe formed bag stack. The device: comprises an endless belt on which thebags are stacked, an adjustableposition stop 2 against which the bagscome to stop by the stacking thereof as well as a fixed stop 3, thespacing between both said stops being set according to the bagdimensions in such a way that said spacing be substantially equal tothat bag dimension in parallel relationship with the lengthwise axis ofbelt 1. The movernents of belt 1 are intermittent and they arecontrolled in a way known per se, from a motor with reduction gearing 4and through a bag-counting apparatus (not shown), said apparatus alsoacting on the control means for the stop 2 which are so synchronizedwith the control means for belt 1 as to impart thereto an alternatingmotion to cause the stop 2 to move away from the belt to leave a passagebetween said stop and belt 1 so as to allow the removal of a formed bagstack, and to return afterwards to its position against said belt, thebelt movement only occuring when the stop 2 has completely released thepassage for the bag stack. The de' vice control means are so arranged asto act upon the bag-forming machine control means to stop said machinewhen the belt is driven. However with low production rate machines, itis possible to perform the stacking device cycle during the formation ofa bag. In such a case, the machine does not have to be stopped duringthe movement operations for the already formed bag stack. To preventspreading of the bag stack on belt 1 as said belt starts to move, thedevice comprises means 5 arranged to bear on the stack upper side whensaid stack is formed and before belt 1 starts to move, control means 6being provided to impart an alternating motion to said bearing means soas to bring them towards and away from the bag stack, said bags being soarranged that the area thereof engaging the upper'side of the stack ofbags 7 (shown in dotted lines in FIG. 1) moves with the same linearspeed as the belt 1 and along the same direction as said belt. The means5 advantageously comprise a cylinder 8 in parallel relationship with thebelt 1 and with the axis thereof at right angle to the movementdirection of said belt, said cylinder 8 being mounted on a shaft 9 insuch a way that said cylinder rotates freely on said shaft. The controlmeans 10 for imparting to the stop 2 said alternating motion and thecontrol means 6 for the alternating motion of cylinder 8 comprise forbringing same away from and nearer to the belt 1, in oppositedirections, in such a way that said cylinder bears on the stack when thestop 2 has released a passage thereon, a single driving member 12. Thestop 2 is arranged on two uprights l3 and 13' while the cylinder isarranged on two up rights 14, 14', said uprights I3, l3, l4, 14' beingin parallel relationship and so guided as to be simultaneously movableby pairs (13, 13) and (l4, 14) along the lengthwise axis thereof whichlies substantially at right angle to that plane going through side 15 ofbelt 1, each one of said uprighs being provided with a rack 16, theracks 16 of the upright pairs (13, 14) and (13', 14) facing one anotherand a pinion l7 meshing with both racks 16 of each one of said lastupright pairs located on either side of belt 1 so as to movesimultaneously the uprights of each pair (13, 14) and (13', 14') alongopposite directions, both pinions 17 being made fast to a single shaft18 which is rotated by means of a rack 19, which meshes with a gearwheel 20 integral with shafts 18, said driving member 12 beingadvantageously operated by a jack 21 which bears on the piston rodthereof, the rack 19. Each pair of said uprights (13, 14) (13', 14') isarranged on a frame 22 which is so movable as to adjust the position ofstop 2 according to the bag dimensions, said frames 22 being joinedtogether so as to move simultaneously and in parallel relationship withthe movement direction of belt 1 under the action of pinions 23 drivenby a handwheel 24 and which mesh with two racks 25 which are attached tothe device frame 24. Cylinder 8 might under the action of the bag stackon which it bears, be rotated by friction about the axis thereof withthe same linear speed as the belt 1 and thus retain the bag stackperfectly formed and this due to said stack being clamped between thecylinder 8 and belt 1. In the embodiment of the device shown in thedrawings, cylinder 8 is so arranged as to be positively driven from thepower cylinder 27 and by motor 4 and chain 28, with the same linearspeed and along the same direction as belt I. Said positive driving ofcylinder 8 is performed by means of two belts 29 arranged on either sideof endless belt 1 in parallel relationship therewith, cooperating withcylinder 27 and so arranged as to have the portions 30 thereof extendingon the path of cylinder 8 when said cylinder moves to bear on the bagstack, said cylinder 8 thus being driven by friction by the belts assoon as endless belt 1 moves to discharge a bag stack. Return pulleys 31are provided for the belts 29 on the frames 22, said belts beingprovided as well as endless belt 1, with a spring tensioning device (notshown). The control means for jack 2] attached to one frame 22, and thecontrol means for motor 4 are so arranged that said motor is energizedto drive belt 1, belts 29 and cylinder 8 when said jack has brought saidcylinder in engagement with the bag stack and belts 29 and when stop 2has released belt 1. The stacking device further comprisesadvantageously a blowing ramp 32 which is arranged in parallelrelationship and crosswise to the belt 1 between the outlet of thebag-forming machine and stop 2, said ramp supplied with lowpressure airbeing so directed as to rapidly bring the bags down on belt 1 or on thebag stack being formed and thus to prevent with a high production rateof the machine, the bags floating and colliding with the following bagsbefore laying said bags down on the stack.

The device according to the invention and shown in FIG. 3 is so designedas to allow the formation ofa bag stack and the stocking on endless belt1, of a determined number of formed stacks. To retain said formed bagstacks perfectly arrayed by the intermittent movements of belt 1,auxiliary cylinders 8 are associated to cylinder 8, the total number ofcylinders being equal to the number less one of bag stacks to be stockedon belt 1 so as to release that bag stack fartest away from cylinder 8and to cooperate with each formed stack in the same way as the cylinder8 acting upon the newlyformed stack, said cylinders 8 and 8 beingparallel, lying at the same level and being regularly spaced from oneanother in such a way that each one of said cylinders might bear on theupper side of the corresponding stack of bags 7 substantially in thesame location on said side, means 33 and 34 being provided to operatethe cylinders 8' in sucha way that the movements thereof be identicaland simultaneous with the movements of cylinder 8. To allow adjustingthe position of cylinders 8 according to the bag dimensions. eachcylinder 8 is mounted on two parallel uprights l3, 13' similar to thoseuprights which support cylinder 8, said uprights 13, 13 for eachcylinder 8 being arranged on a movable frame 35 which is controlled soas to move in parallel relationship with the lengthwise axis of belt 1,by a pinion 36 which is controlled by a hand wheel 37 and which mesheswith the rack 25 attached to the device frame 26. Said means 33 areprovided to rotate about the shaft 9' thereof the cylinders 8 with thesame speed as cylinder 8 and said means 33 comprise on the one hand abelt 38 cooperating with each one of cylinders 8 and 8 and driven bycylinder 8 and on the other hand, a resilient member 39 insuringtensioning of said belt 38 whatever he the spacing between cylinders 8and 8. Means 34 are provided to control the upwards and downwardsmovement of cylinders 8 from gear wheel 20 which controls cylinder 8 andsaid means comprise on the one hand a chain 40 cooperating with each oneof pinions 41 provided for driving at the same speed, those uprights l3,13 which support cylinders 8 and on the other hand, a resilient member42 insuring tensioning of chain 40 whatever be the spacing betweencylinders 8 and 8.

It must be understood that the invention is in no way limited to theabove embodiments and that many changes may be brought therein withoutdeparting from the scope of the invention as defined by the appendedclaims.

I claim:

1. A device to be arranged at the outlet of a bagshaping machine forallowing the formation of a bag stack and the removal of the formed bagstack, said device comprising and endless conveying belt on which thebags are stacked, belt control means to impart to said belt anintermittent movement through, a bag stack measuring device, a stopextending cross-wise to the belt'movement direction and against whichthe bag stack is formed, and stop control means synchronized with thebelt control means for imparting to the stop an alternating motion so asto release the formed bag stack and allow the removal thereof by saidbelt, bearing means so arranged as to bear on the upper side of the bagstack when said stack is formed, and when said stop control meansreleases the formed bag stack, bearing control means being provided toimpart to said bearing means an alternating motion to move same towardsand away from said upper side, said bearing means being so arranged thatthe part thereof engaging the bag stack upper side moves with the samelinear speed as the endless belt and along the same direction as saidbelt to prevent spreading of the bag stack on said belt.

2. Device as claimed in claim 1, in which second control means areprovided to positively drive the bearing means with the same linearspeed as the endless belt and along the same direction as said belt.

3. Device as claimed in claim 2, in which the endless belt control meansand the bearing means second con trol means comprise a single drivingmember for driving the belt and said bearing means in the same directionand with the same linear speed.

4. Device as claimed in claim 2, in which said bearing means comprise atleast one cylinder in parallel relationship with the belt and with theaxis thereof at right angle to the endles belt moving direction, saidcylinder being so mounted on a shaft as to rotate freely about the axisthereof.

5. Device as claimed in claim 4, in which said cylinder is arranged ontwo parallel uprights. guides being provided to allow said uprights tomove simultaneously under the action of said bearing control means,along the lengthwise axis thereof which is substantially at right angleto that plane going through that endless belt side on which the bags arestacked.

6. Device as claimed in claim 1, which comprises a blowing ramp arrangedin parallel relationship and cross-wise to the endless conveying beltbetween the bag-forming machine outlet and said stop, said ramp being sodirected as to bring the bags down on the conveying belt and on a bagstack being formed.

7. Device as claimed in claim 1, in which a fixed stop is provided inparallel relationship with the movable stop, between said movable stopand the bag-forming machine outlet, the spacing between both said stopscorresponding substantially to the dimension of one bag in parallelrelationship with the endless conveying belt lengthwise axis.

8. A device to be arranged at the outlet of a bagshaping machine forallowing the formation of a bag stack and the removal of the formed bagstack, said device comprising: an endless conveying belt on which thebags are stacked; belt control means to impart to said belt anintermittent movement through; a bag stack measuring device a stopextending cross-wise to the belt movement direction and against whichthe bag stack is formed; stop control means synchronized with the beltcontrol means for imparting to the stop an alternating motion so as torelease the formed bag stack and allow the removal thereof by said belt;bearing means so arranged as to bear on the upper side of the bag stackwhen said stack is formed and when said stop control means releases theformed bag stack; bearing control means provided to impart to saidbearing means an alternating motion to move same towards and away fromsaid upper side, said bearing means being so arranged that the partthereof engaging the bag stack upper side moves with the same linearspeed as the endless belt and along the same direction as said belt toprevent spreading of the bag stack on said belt, said stop control meansand said bearing control means being synchronized and comprising asingle driving member and being so arranged that the bearing means bearon the bag stack upper side when the stop retaining the stack has beencompletely separated from the endless belt and has released the bagstack.

9. A device to be arranged at the outlet of a bagshaping machine forallowing the formation of a bag stack and the removal of the formed bagstack, said device comprising: an endless conveying belt on which thebags are stacked, said belt being looped over a driven cylinder; beltcontrol means to impart to said belt an intermittent movement through abag stack measuring device; a stop extending cross-wise to the beltmovement direction and against which the bag stack is formed; stopcontrol'means synchronized with the belt control means for imparting tothe stop an alternating motion so as to release the formed bag stack andallow the removal thereof by said belt; bearing means including a freelyrotating cylinder disposed parallel to and transverse to said belt andarranged to bear on the upper side of the bag stack when said stack isformed and when said stop control means releases the formed bag stack;bearing control means being provided to impart to said bearing means analternating motion to move same towards and away from said upper side;second control means to positively drive the bearing means so that thefreely rotating cylinder engaging the bag stack upper side moves withthe same linear speed as the endless conveying belt and in the samedirection as said belt to prevent spreading of the bag stack on saidbelt, endless conveying said second control means comprising at leastone belt in parallel relationship with the said endless conveying beltand driven by said driven cylinder, said one belt being so arranged asto have a portion thereof extending in the path of the freely rotatingcylinder when the latter moves to bear on the bag stack, said freelyrotating cylinder being driven by friction by said one belt when saidendless conveying belt is operated to move the formed bag stack.

10. A device to be arranged at the outlet of a bagshaping machine forallowing the formation of a bag stack and the removal of the formed bagstack, said device comprising: an endless conveying belt onwhich thebags are stacked; belt control means to impart to said belt anintermittent movement through a bag stack measuring device; a stopsupported by two parallel first uprights and extending cross-wise to thebelt movement direction and against which the bag stack is formed;guides for guiding the uprights for movement along paths coinciding withtheir axes; a facing rack carried by each of said guides; stop controlmeans synchronized with the belt control means: for imparting to thestop an alternating motion so as to release the formed bag stack andallow ,the removal thereof by said belt; bearing means including twoparallel second uprights supporting a freely rotating cylinder which isdisposed parallel to and transverse to said belt and arranged to bear onthe upper side of the bag stack when said stack is formed and when saidstop control means releases the formed bag stack, said bearing meansfurther including guides for guiding the uprights to move along pathscoinciding with their axes; a facing rack carried by each of saidlast-named guides; pinion means associated with all said facing racksfor moving said first and second uprights in opposite directions; stopcontrol means being provided to impart to said bearing means analternating motion to move same towards and away from said upper side;second control means to positively move the bearing means so that thefreely rotatable cylinder engaging the bag stack upper side moves withthe same linear speed as the endless conveying belt and in the samedirection as said belt to prevent spreading of the bag stack on saidbelt.

11. A device as claimed in claim 10, in which each said upright pairs isarranged on a frame which is movable so as to allow adjusting the stopposition according to the bag size, said frames being joined together soas to move simultaneously in parallel relationship with the endless beltmovement direction under the action of at least one pinion meshing witha rack attached to the device frame.

12. A device to be arranged at the outlet of a bagshaping machine forallowing the formation of a bag stack and the removal of the formed bagstack, said device comprising: an endless conveying belt on which thebags are stacked, control means to impart to said belt an intermittentmovement through a bag stack measuring device; a stop extendingcross-wise to the belt movement direction and against which the bagstack is formed; stop control means synchronized with the belt controlmeans for imparting to the stop an alternating motion so as to releasethe formed bag stack and allow the removal thereof by said belt; bearingmeans including a freely rotating cylinder disposed parallel to andtransverse to said belt and arranged to bear on the upper side of thebag stack when said stack is formed, when said stop control meansreleases the formed bag stacks; bearing control means being provided toimpart to said bearing means an alternating motion to move same towardsand away from said upper side; second control means to positively drivethe bearing means so that the freely rotating cylinder engaging the bagstack upper side moves with the same linear speed as the endlessconveying belt and in the same direction as said endless conveying beltto prevent spreading of the bag stack on said belt; and auxiliarycylinders associated with said freely rotating cylinder, the totalnumber of cylinders being equal to the number less one of the bag stacksto be stacked on said conveying belt, said cylinders being in parallelrelationship, located at the same level and regularly spaced from oneanother in such a way that each cylinder may bear on the correspondingstack upper side substantially in the same location on said side; andmeans to operate the auxiliary cylinders in such a way that themovements thereof are identical and simultaneous with the movements ofthe freely rotating cylinder.

13. A device as in claim 12, in which each one of the auxiliarycylinders associated with said freely-rotating cylinder is mounted ontwo parallel uprights similar to the uprights supporting said freelyrotating cylinder, the uprights of each said auxiliary cylinders beingarranged on a movable frame so as to allow adjusting the cylinderposition according to the bag size, each frame being controlled for amovement in parallel relationship with the conveying belt movement, by apinion meshing with a rack attached to the device frame.

14. A device to be arranged at the outlet of a bagshaping machine forallowing the formation of a bag stack and the removal of the formed bagstack, said device comprising a conveyor on which the bags are stacked,conveyor control means to impart to said conveyor an intermittentmovement through a bag stack measuring device, a stop extendingcross-wise to the conveyor movement direction and against which the bagstack is formed, and stop control means synchronized with the conveyorcontrol means for imparting to the stop an alternating motion so as torelease the formed bag stack and allow the removal thereof by saidconveyor, bearing measn so arranged as to bear on the upper side of thebag stack when said stack is formed and when said stop control meansreleases the formed bag stack, bearing control means being provided toimpart to said bearing means an alternating motion to move said bearingmeans towards and away from said upper side of said bag stack, saidbearing means being so arranged that the part thereof engaging the upperside of the bag stack moves with the same speed as the conveyor andalong the same direction of movement as the conveyor to preventspreading of the bag stack on the conveyor.

1. A device to be arranged at the outlet of a bag-shaping machine forallowing the formation of a bag stack and the removal of the formed bagstack, said device comprising and endless conveying belt on which thebags are stacked, belt control means to impart to said belt anintermittent movement through, a bag stack measuring device, a stopextending cross-wise to the belt movement direction and against whichthe bag stack is formed, and stop control means synchronized with thebelt control means for imparting to the stop an alternating motion so asto release the formed bag stack and allow the removal thereof by saidbelt, bearing means so arranged as to bear on the upper side of the bagstack when said stack is formed, and when said stop control meansreleases the formed bag stack, bearing control means being provided toimpart to said bearing means an alternating motion to move same towardsand away from said upper side, said bearing means being so arranged thatthe part thereof engaging the bag stack upper side moves with the samelinear speed as the endless belt and along the same direction as saidbelt to prevent spreading of the bag stack on said belt.
 2. Device asclaimed in claim 1, in which second control means are provided topositively drive the bearing means with the same linear speed as theendless belt and along the same direction as said belt.
 3. Device asclaimed in claim 2, in which the endless belt control means and thebearing means second control means comprise a single driving member fordriving the belt and said bearing means in the same direction and withthe same linear speed.
 4. Device as claimed in claim 2, in which saidbearing means comprise at least one cylinder in parallel relationshipwith the belt and with the axis thereof at right angle to the endlesbelt moving direction, said cylinder being so mounted on a shaft as torotate freely about the axis thereof.
 5. Device as claimed in claim 4,in which said cylinder is arranged on two parallel uprights, guidesbeing provided to allow said uprights to move simultaneously under theaction of said bearing control means, along the lengthwise axis thereofwhich is substantially at right angle to that plane going through thatendless belt side on which the bags are stacked.
 6. Device as claImed inclaim 1, which comprises a blowing ramp arranged in parallelrelationship and cross-wise to the endless conveying belt between thebag-forming machine outlet and said stop, said ramp being so directed asto bring the bags down on the conveying belt and on a bag stack beingformed.
 7. Device as claimed in claim 1, in which a fixed stop isprovided in parallel relationship with the movable stop, between saidmovable stop and the bag-forming machine outlet, the spacing betweenboth said stops corresponding substantially to the dimension of one bagin parallel relationship with the endless conveying belt lengthwiseaxis.
 8. A device to be arranged at the outlet of a bag-shaping machinefor allowing the formation of a bag stack and the removal of the formedbag stack, said device comprising: an endless conveying belt on whichthe bags are stacked; belt control means to impart to said belt anintermittent movement through; a bag stack measuring device a stopextending cross-wise to the belt movement direction and against whichthe bag stack is formed; stop control means synchronized with the beltcontrol means for imparting to the stop an alternating motion so as torelease the formed bag stack and allow the removal thereof by said belt;bearing means so arranged as to bear on the upper side of the bag stackwhen said stack is formed and when said stop control means releases theformed bag stack; bearing control means provided to impart to saidbearing means an alternating motion to move same towards and away fromsaid upper side, said bearing means being so arranged that the partthereof engaging the bag stack upper side moves with the same linearspeed as the endless belt and along the same direction as said belt toprevent spreading of the bag stack on said belt, said stop control meansand said bearing control means being synchronized and comprising asingle driving member and being so arranged that the bearing means bearon the bag stack upper side when the stop retaining the stack has beencompletely separated from the endless belt and has released the bagstack.
 9. A device to be arranged at the outlet of a bag-shaping machinefor allowing the formation of a bag stack and the removal of the formedbag stack, said device comprising: an endless conveying belt on whichthe bags are stacked, said belt being looped over a driven cylinder;belt control means to impart to said belt an intermittent movementthrough a bag stack measuring device; a stop extending cross-wise to thebelt movement direction and against which the bag stack is formed; stopcontrol means synchronized with the belt control means for imparting tothe stop an alternating motion so as to release the formed bag stack andallow the removal thereof by said belt; bearing means including a freelyrotating cylinder disposed parallel to and transverse to said belt andarranged to bear on the upper side of the bag stack when said stack isformed and when said stop control means releases the formed bag stack;bearing control means being provided to impart to said bearing means analternating motion to move same towards and away from said upper side;second control means to positively drive the bearing means so that thefreely rotating cylinder engaging the bag stack upper side moves withthe same linear speed as the endless conveying belt and in the samedirection as said belt to prevent spreading of the bag stack on saidbelt, endless conveying said second control means comprising at leastone belt in parallel relationship with the said endless conveying beltand driven by said driven cylinder, said one belt being so arranged asto have a portion thereof extending in the path of the freely rotatingcylinder when the latter moves to bear on the bag stack, said freelyrotating cylinder being driven by friction by said one belt when saidendless conveying belt is operated to move the formed bag stack.
 10. Adevice to be arranged at the outlet of a bag-shaping machine forallowing the formation Of a bag stack and the removal of the formed bagstack, said device comprising: an endless conveying belt on which thebags are stacked; belt control means to impart to said belt anintermittent movement through a bag stack measuring device; a stopsupported by two parallel first uprights and extending cross-wise to thebelt movement direction and against which the bag stack is formed;guides for guiding the uprights for movement along paths coinciding withtheir axes; a facing rack carried by each of said guides; stop controlmeans synchronized with the belt control means for imparting to the stopan alternating motion so as to release the formed bag stack and allowthe removal thereof by said belt; bearing means including two parallelsecond uprights supporting a freely rotating cylinder which is disposedparallel to and transverse to said belt and arranged to bear on theupper side of the bag stack when said stack is formed and when said stopcontrol means releases the formed bag stack, said bearing means furtherincluding guides for guiding the uprights to move along paths coincidingwith their axes; a facing rack carried by each of said last-namedguides; pinion means associated with all said facing racks for movingsaid first and second uprights in opposite directions; stop controlmeans being provided to impart to said bearing means an alternatingmotion to move same towards and away from said upper side; secondcontrol means to positively move the bearing means so that the freelyrotatable cylinder engaging the bag stack upper side moves with the samelinear speed as the endless conveying belt and in the same direction assaid belt to prevent spreading of the bag stack on said belt.
 11. Adevice as claimed in claim 10, in which each said upright pairs isarranged on a frame which is movable so as to allow adjusting the stopposition according to the bag size, said frames being joined together soas to move simultaneously in parallel relationship with the endless beltmovement direction under the action of at least one pinion meshing witha rack attached to the device frame.
 12. A device to be arranged at theoutlet of a bag-shaping machine for allowing the formation of a bagstack and the removal of the formed bag stack, said device comprising:an endless conveying belt on which the bags are stacked, control meansto impart to said belt an intermittent movement through a bag stackmeasuring device; a stop extending cross-wise to the belt movementdirection and against which the bag stack is formed; stop control meanssynchronized with the belt control means for imparting to the stop analternating motion so as to release the formed bag stack and allow theremoval thereof by said belt; bearing means including a freely rotatingcylinder disposed parallel to and transverse to said belt and arrangedto bear on the upper side of the bag stack when said stack is formed,when said stop control means releases the formed bag stacks; bearingcontrol means being provided to impart to said bearing means analternating motion to move same towards and away from said upper side;second control means to positively drive the bearing means so that thefreely rotating cylinder engaging the bag stack upper side moves withthe same linear speed as the endless conveying belt and in the samedirection as said endless conveying belt to prevent spreading of the bagstack on said belt; and auxiliary cylinders associated with said freelyrotating cylinder, the total number of cylinders being equal to thenumber less one of the bag stacks to be stacked on said conveying belt,said cylinders being in parallel relationship, located at the same leveland regularly spaced from one another in such a way that each cylindermay bear on the corresponding stack upper side substantially in the samelocation on said side; and means to operate the auxiliary cylinders insuch a way that the movements thereof are identical and simultaneouswith the movements of the freely rotating cylinder.
 13. A device as inclaim 12, in which each one of the auxiliary cylinders associated withsaid freely-rotating cylinder is mounted on two parallel uprightssimilar to the uprights supporting said freely rotating cylinder, theuprights of each said auxiliary cylinders being arranged on a movableframe so as to allow adjusting the cylinder position according to thebag size, each frame being controlled for a movement in parallelrelationship with the conveying belt movement, by a pinion meshing witha rack attached to the device frame.
 14. A device to be arranged at theoutlet of a bag-shaping machine for allowing the formation of a bagstack and the removal of the formed bag stack, said device comprising aconveyor on which the bags are stacked, conveyor control means to impartto said conveyor an intermittent movement through a bag stack measuringdevice, a stop extending cross-wise to the conveyor movement directionand against which the bag stack is formed, and stop control meanssynchronized with the conveyor control means for imparting to the stopan alternating motion so as to release the formed bag stack and allowthe removal thereof by said conveyor, bearing measn so arranged as tobear on the upper side of the bag stack when said stack is formed andwhen said stop control means releases the formed bag stack, bearingcontrol means being provided to impart to said bearing means analternating motion to move said bearing means towards and away from saidupper side of said bag stack, said bearing means being so arranged thatthe part thereof engaging the upper side of the bag stack moves with thesame speed as the conveyor and along the same direction of movement asthe conveyor to prevent spreading of the bag stack on the conveyor.